The ability to increase the data storage capacity in magnetic recording processes is an ongoing concern. As the amount of information to be stored continues to increase, the demand for higher density recording also continues to increase. Heat assisted magnetic recording (HAMR) is a proposed technology for increasing the storage density of conventional magnetic recording devices. Heat assisted magnetic recording combines facets of both optical and magnetic recording in an effort to increase storage capacity.
Conventional hard disc drives rely on a magnetic field produced by a small recording pole formed on a recording head. The recording head and recording pole are on a slider that “flies” across the surface of the disc as the disc spins. The magnetic field from the small recording pole needs to be sufficient to overcome the coercivity of the magnetic recording medium in the disc in order to define the recorded bits along the recording track in the recording medium.
As the storage density of disc drives increases, the size of the recorded bits in the recording medium must correspondingly decrease. Additionally, the individual magnetic grains which make up a recorded bit must also decrease in size to maintain approximately the same number of magnetic grains per bit cell in order to ensure a sufficient signal-to-noise ratio (SNR). However, as the size, and hence the volume, of the magnetic grains decrease, the thermal stability of the grains will also decrease unless the coercivity of the recording medium is increased. Thus, improved thermal stability is required in order to manufacture magnetic recording media for higher storage densities, such that, when the media is written upon, the recorded bits should not change magnetization direction simply by thermal fluctuations.
In order to provide for increased thermal stability, it is necessary to provide a recording medium having a high crystalline anisotropy (Ku). Such materials will also have a high coercivity and will be much more difficult to magnetize than conventional recording media. Heat assisted magnetic recording is one proposed technique for overcoming this difficulty. It is known that the coercive force of the recording media is lowered with elevated temperature. Therefore, if the temperature of the recording media is raised during writing, it will be possible to write information on the disc with a lesser strength magnetic field than if the recording media were not heated. When the recording media is subsequently cooled, the information on the media is thermally stable due to the high coercivity of the media. Heat assisted magnetic recording reduces the coercivity of the magnetic grains during recording by optically heating the spot to be recorded. However, in order to do this, the heat, i.e., light, and the magnetic field must be delivered coincident at the same location on the recording media.
The present invention is directed toward overcoming one or more of the above-mentioned problems.